Péclet Number Calculator
Enter velocity, characteristic length and thermal/mass diffusivity to compute the Péclet number Pe = v·L/D.
Input Data
Results
At a glance:The Péclet number Pe = v·L/D compares advective (bulk flow) transport to diffusive transport, with v velocity, L a characteristic length and D the relevant diffusivity (α for heat, D_m for mass). High Pe (≫1) means advection dominates — sharp fronts, little smearing; low Pe (≪1) means diffusion smooths the field. It relates to other groups: Pe = Re·Pr (thermal, since Re·Pr = vL/ν · ν/α = vL/α) and Pe = Re·Sc (mass). In microfluidics and chemical reactors it tells whether mixing is convection- or diffusion-limited. This tool computes Pe = vL/D from v, L, D.
Formula
Pe = v·L/D
Pe = Re·Pr (thermal), Pe = Re·Sc (mass)
$$\mathrm{Pe} = \mathrm{Re}\cdot\mathrm{Pr} = \dfrac{v\,L}{\alpha}$$How to Use
- Enter velocity v (m/s).
- Enter characteristic length L (m) and diffusivity D (m²/s).
- The calculator returns Pe.
Case Studies
River mixing
v = 0.5 m/s, L = 10 m, D = 0.01 m²/s.
Pe = 0.5×10/0.01 = 500.
Advection-dominated; plume stays narrow.
FAQ
What does a high Péclet number mean?
Advection dominates over diffusion — transported quantities move mainly by bulk flow with little spreading; mixing is slow unless stirred.
How is it related to Reynolds and Prandtl?
Pe = Re·Pr for heat (and Re·Sc for mass), combining inertial/viscous and transport-ratio effects.
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References
Content review: Calculatorism Editorial Team. Results are for reference only; please refer to the relevant authorities for the official figures.